The invention concerns a procedure for loading a piston-cylinder unit with fluid under pressure, primarily for use in the manufacture of motor vehicle bodywork.
The invention also concerns a control module for loading a piston-cylinder unit with fluid under pressure, primarily for use in the manufacture of motor vehicle bodywork.
The invention also concerns a piston-cylinder unit as a working cylinder to be loaded with fluid under pressure, primarily for use in the manufacture of motor vehicle bodywork.
Finally, the invention concerns the use of a working cylinder of this kind to power devices for tensioning and/or compressing and/or joining and/or stamping and/or embossing and/or punching and/or welding, if necessary, under the interposition of a toggle joint or other gearing parts, e.g. for use in the manufacture of motor vehicle bodywork.
Piston-cylinder units are referred to in the industry for short as “working cylinders”. Where the term “working cylinder” is used in the following, it is understood to mean not only a cylinder but also an operable drive unit comprising at least one cylinder and at least one piston guided in this cylinder so as to be longitudinally displaceable and to seal it and having a piston rod disposed on one side of the said piston, which piston rod is preferably sealed and made to project from the said cylinder chamber and which powers devices primarily for tensioning and/or compressing and/or joining and/or stamping and/or embossing and/or punching and/or welding. In the case of such devices e.g. the piston rod often drives under interposition of at least one toggle joint other device parts such as a tensioning arm which cooperates with an opposing member or an expanding mandrel or a centring mandrel or a jointing device or a stamp, a device part for punching or also device parts, for example, under interposition of a toggle joint, actuatable welding electrodes.
Devices for tensioning, compressing, joining, stamping, embossing, punching and welding are used in many forms in, for example, the manufacture of motor vehicle bodywork. Tensioning devices are often constructed as “toggle tensioning devices” and hold body sheets in position until they are permanently fastened on by means of spot-welding, adhesion, clinching, etc., while other devices, for example, function as under-floor clamps and power a centring mandrel under interposition of a link mechanism, e.g. a parallelogram gear, to align one with the other and centre a number of sheets. Examples of these are to be found in, amongst others, catalogs of Tünkers Maschinenbau GmbH “Product Range”, “Tensioning Technology for Professional Series Manufacture”, “Tensioning Systems, Handling, Forming Technology, Stamping, Edging, Pressure Joining, Embossing” and in patent specifications DE 196 16 441 C1, DE 198 24 579 C1 and DE 199 30 990 C1.
In all these procedures, control systems, working cylinders and devices full pressure is need only for the last part of the working stroke. This means that for 90 percent and more of the setting stroke of the piston concerned and its piston rod—idle stroke—only a weak force is necessary, for example, to overcome friction and certain mass inertia and gravitational forces. Supply with fluid under pressure, for example, hydraulic fluid or compressed air and so the pump output and its driving power, however, is in the present state of the art needed for the entire stroke of the assigned piston with piston rod, for example, toggle joint and the like, which means that the greater part of the driving power is lost.